Direct C–H Alkenylation of Functionalized Pyrazoles

We have developed inter- and intramolecular C–H alkenylation reactions of pyrazoles. The catalyst, derived from Pd­(OAc)2 and pyridine, enabled the oxidative alkenylation of pyrazoles containing a variety of functional groups at the C4 position. Activated alkenes, including acrylate, acrylamide, and styrene derivatives, and enamides could be installed in this process. The sequential C–H alkenylation and cyclization reactions gave rise to fused bicyclic pyrazoles, providing a new strategy to annulate readily available pyrazole compounds.